Sub-second ultrafast yet programmable wet-chemical synthesis

Wet-chemical synthesis via heating bulk solution is powerful to obtain nanomaterials. However, it still suffers from limited reaction rate, controllability, and massive consumption of energy/reactants, particularly for the synthesis on specific substrates. Herein, we present an innovative wet-interfacial Joule heating (WIJH) approach to synthesize various nanomaterials in a sub-second ultrafast, programmable, and energy/reactant-saving manner. In the WIJH, Joule heat generated by the graphene film (GF) is confined at the substrate-solution interface. Accompanied by instantaneous evaporation of the solvent, the temperature is steeply improved and the precursors are concentrated, thereby synergistically accelerating and controlling the nucleation and growth of nanomaterials on the substrate. WIJH leads to a record high crystallization rate of HKUST-1 (~1.97 μm s−1), an ultralow energy cost (9.55 × 10−6 kWh cm−2) and low precursor concentrations, which are up to 5 orders of magnitude faster, −6 and −2 orders of magnitude lower than traditional methods, respectively. Moreover, WIJH could handily customize the products’ amount, size, and morphology via programming the electrified procedures. The as-prepared HKUST-1/GF enables the Joule-heating-controllable and low-energy-required capture and liberation towards CO2. This study opens up a new methodology towards the superefficient synthesis of nanomaterials and solvent-involved Joule heating.

1. Considering the previous publications on the Joule heating method, the authors are required to add more recent related progresses. Moreover, the main differences and the novelty of this work should be highlighted in the introduction part. 2. Fig. 2c and 2b are hard to understand and authors should add the relevant description of the symbols in the Figures, such as the C, Cs, and h0. In addition, the detailed experiment content about how to get the h in Fig. 2b and how to get the density in Fig. 2c should be provided in manuscript or supplementary information. 3. Authors have discussed the WIJH synthesis mechanism and the difference on the growth of HKUST-1 for the various synthesis conditions, have some different found in nucleation or growth mechanism for the WIJH compared with the conventional bulk-heating-based methods or solvothermal method? 4. How did authors obtain the specific value of the normalized quantity in Fig. 3a? 5. Achieving the large-scaled synthesis using Joule heating method is significant for industrial production, thus I recommend that the authors provide more experiment content and discussion on the roll-to-roll Joule-heating continuous fabrication. 6. As the control experiment, the performance of the CO2 capture and liberation for the HKUST-1/GF synthesized by conventional method should be added and discussed.
Reviewer #2 (Remarks to the Author): This manuscript reports the synthesis of materials using Joule heating method. These materials are often prepared by the wet-chemistry that involves a longer synthesis time and large usage of reactants/solvent etc. By placing a thin layer of synthesis precursor on the heating medium, a carbon file, the authors claimed that the materials including MOFs, COF, metal, metal oxide and sulfide were prepared within sub-second. Overall this is a very interesting work since the synthesis method is new and the formed materials morphology is quite different from the conventional thermal synthesis. Specific comments are listed below.
(1) The materials synthesized by this Joule heating method are simple and easy to crystallize. For example, ZIF-8, HKUST etc does not need very harsh conditions to synthesize. From this point of view, it is hard to see the obvious advantages of the Joule heating method for wet-chemistry synthesis of solid materials.
(2) The materials' synthesis solution is quick small. During the Joule heating, the evaporation of solvent should have a significant effects on the materials crystallization and growth. The authors mentioned a bit on this effect, but I think this effect should be more obvious than what has been claimed in the manuscript. Control experiments should be done to clarify the dominating mechanism (e.g., Joule heating versus solvent evaporation) in the synthesis.
(3) In line 157, the nucleation equation, I think there should be a negative sign in the exponent. Otherwise, the dependence on Temperature and supersaturation does not seem to be correct.
(4) How did the authors get the growth rate in the synthesis? The heating and cooling is fast which needs techniques to capture these temperature profiles precisely. On the basis of this, is it possible to get the rate. How does the temperature ramp up and down affect the growth?
Reviewer #3 (Remarks to the Author): In this work, Zhang et al. reported a wet-interfacial Joule heating approach for synthesis of nanomaterials on conductive carbon films like graphene films. A very thin liquid layer is coated on the graphene film and the Joule heating rapid bring it to a high temperature to trigger the reaction. They synthesized various nanomaterials such as MOF, COF, metal nanoparticles, oxide nanoparticles, etc. And they demonstrated the application of the MOF films for CO2 uptake and the application of the Joule heating method for temperature swing adsorption. Main concerns: 1. One main concern of this method is the scalability. The reaction happens at the interface between the graphene film and the solution; thus, the solution must be a very thin layer. This seriously limit its production rate and scalability compared to the bulk solution synthesis method.                 demonstrate some strategies to scale up the process? Maybe a continuous process? 2. The synthesized materials are loaded onto the graphene films substrates. Is there any appropriate method to separate the synthesized materials and the heating substrates? 3. In Supplementary Table 2, the authors compared the energy cost, time consumption, etc., for a batch between the reported method here with literature routes. However, I recommend to normalize to the mass per batch since different literature routes obtained different amounts of                  mL synthesis. 4. The particle size of MOF synthesized by this method is a few hundreds of nanometer. What's the size controllability of this method? Could it be used to synthesize MOF nanoparticles (<100 nm) or large crystals? 5. The authors demonstrate the CO2 uptake and liberation cycle by the Joule heating process ( Figure 5). What is the mechanism of the Joule heating-induced liberation? 6. What is the energy cost of the Joule heating induced CO2 desorption and how does it compare to temperature swing enabled by other thermal processes, as well as other pressure swing process? 7. Will the precursors also be evaporated during the synthesis process since the synthesis temperature is so high (>300°C)? And the organics maybe be destroyed under this high temperature. Minor points: 1. Supplementary Fig. 5 is not discussed in the main text. 2. Line 217, the authors mentioned that the particles could fuse together to form a film consisting of monolayer MOF particles. There is no evidence that the film is "monolayer". 3. PDF reference card should be provided for all the XRD patterns.

Responses to Reviewer #1:
This manuscript reports a wet-interfacial Joule heating (WIJH) approach to synthesize nanomaterials in a sub-second ultrafast, programmable, and energy/reactant-saving manner. Using this method, authors also demonstrate the successful synthesis of the metal-organic framework, covalent-organic framework, metal, metal oxide and sulfide in an ultralow energy cost and a high growth rate. Compared with the traditional thermal treatment approaches, the Joule heating displays the great advantages in synthesis rate and energy cost. In recent years, ultrafast synthesis of nanomaterials by Joule heat has been widely studied, and some researchers also call Joule heating as high-temperature thermal shock method or carbothermal shock. Although the authors have presented the detailed discussion about the universality of this wet-interfacial Joule heating method in material synthesis, this work shows the limited novelty and scientific significance. Thus, I didn't recommend accepting this manuscript for nature communication. R: We sincerely thank the reviewer for the valuable comments and suggestions to help us improve our work. We have tried our best to address these issues and revised the manuscript point-by-point.
We truly understand the reviewer's concern about the novelty and scientific significance of the reported WIJH approach, and we would like to take this opportunity to clearly compare our work with previous significant references about the Joule-heating-based ultrafast synthesis of nanomaterials (Table R1). Differing from recent advances achieved by solid-state reactions in solid-solid systems where only temperature affects the synthesis, our work first realized ultrafast yet programmable liquid-phase wet-chemical synthesis of nanomaterials, based on a new confined interfacial heating mechanism of the synergy between Joule heating (temperature effect) and evaporation (concentration effect). The condition, process, and mechanism for forming nanomaterials from precursor solution are significantly different from those from solid precursors. Thermal conduction in heating liquid (solution) is far from that in heating solid reported in recent works, which is also one of the greatest hindrances in developing highly efficient and controllable wet-chemical synthesis. Moreover, the evaporation-caused concentration effect, another essential factor in reaction kinetics and thermodynamics, is absent or ignored in previous works. How to combine temperature and concentration to accelerate and control the synthesis is significant in both science and industry, but has rarely been reported before. WIJH realized the acceleration and control of the nucleation and growth of nanomaterials on the solidsolution interface within the synergy, enabling a recorded exponential enhancement in the synthesis efficiency and programmable customization of the products' amount, size, and morphology. This work presents a new methodology and technology in both Joule-heating-based and wet-chemical synthesis. Below are the detailed comparison and summary: 1) Recent advances were achieved by Joule-heating-based high and controllable temperature in solid-solid systems Joule heating represents one of the most cutting-edge and advanced technologies nowadays. Benefiting from its superiority in highly-efficient and precise heat output, it has recently initiated a new era of material synthesis. Generally, these reaction systems are constructed by compressing dry and conductive solid precursors between two electrodes or loading dry solid precursors on the electrothermal substrates. Following an instantaneous Joule heating process, the precursors were thermally decomposed/melted/dispersed, and then assembled/reacted into nanomaterials. It shows that these advances were achieved by solid-state reactions in the solid-solid systems, but not in the solid-liquid (solution) system for liquid-phase wet-chemical synthesis. In these systems, within the rapid and highly-efficient heat conduction from the electrothermal materials to the solid precursors, it can achieve high temperature, fast heating/cooling, and precise temperature control over the reaction, thereby using Joule heating (temperature effect) to trigger, accelerate and control the synthesis.
2) Obvious differences of WIJH synthesis in the solid-liquid system in terms of thermal conduction, process, and mechanism for crystallization of nanomaterials However, wet-chemical synthesis, one of the most classic methods to prepare almost all kinds of nanomaterials, has rarely benefited from Joule heating, mainly due to the weakened heat effect in bulk solution. The conditions, processes, and mechanisms for forming nanomaterials from precursor solution are significantly different from those from solid precursors.
Thermal conduction is totally different and more complicated in the solid-liquid (solution) system. When heating liquid (bulk solution), it is hard to achieve high temperature, high ramping/cooling rate, and control of the thermal field. This becomes one of the greatest hindrances to improving the synthesis efficiency and controllability of current wet-chemical synthesis. Through constructing a thin-layer liquid film to confine the Joule heat at the solid-solution interface, our WIJH approach endows the reaction with high temperature (e.g., up to 300 °C for HKUST-1), high ramping (around 300 °C s -1 ) and cooling rates (above 200 °C s -1 ), and sensitive modulation/switch of the temperature. Therefore, we realized the trigger, acceleration, stop, and even control of the reaction in solution through Joule heating.
Moreover, besides Joule heating, the accompanying solvent evaporation also plays a critical role in the WIJH synthesis. It could accelerate the ramping, spatially confine the products around the substrate, and, most importantly, the concentration of the precursors. It is absent or ignored in previous works. How the concentration effect is coupled with the high temperature to accelerate and control the synthesis is significant but has rarely been reported before.
With the synergy between Joule heating (temperature effect) and evaporation (concentration effect) in the new confined interfacial heating mechanism, WIJH realized the acceleration and control of the nucleation and growth of the nanomaterials on the solid-solution interface, enabling a series of record (sub-)second wet-chemical syntheses of various materials. The synthesis efficiency is exponentially enhanced when compared with conventional methods. Moreover, via programming the electrified procedure to control the crystallization, WIJH enabled precise control of the products' amount, size, and morphology. To our knowledge, this has never been realized in conventional bulk-heating-based methods, particularly in such a short second-scale time.
In summary, this work is quite different from the previous works on ultrafast synthesis based on Joule heating. We believe the science of confined wet-interfacial Joule heating to accelerate and control the nucleation and growth, and the combination of super-efficiency, programmability, versatility, and scalability, making our approach a milestone in the research of wet-chemical synthesis and Joule heating, which is worth publishing in Nature Communication. 1. Considering the previous publications on the Joule heating method, the authors are required to add more recent related progresses. Moreover, the main differences and the novelty of this work should be highlighted in the introduction part. R: Thank you. We revised the introduction according to the reviewer's comments and the above discussion. In the revised manuscript, the recent significant advances in Joule-heating-based synthesis have been introduced and cited. The differences and the novelty of our WIJH approach have been emphasized in terms of the unique reaction system of the solid-solution interface, and the new mechanism of confined interfacial heating of the synergy of temperature and concentration effects. These are different from recent advances achieved by the solid-solid systems, in which high and controllable temperature accounts for the acceleration and control of the synthesis. Besides, the results of the exponential enhancement in the synthesis efficiency and the programmability towards the products' amount, size, and morphology have also been highlighted.  (2018)). cn and cs represent the critical concentration of nucleation and the saturation concentration (at which the growth rate equilibrates with the solvation rate), respectively. The red part is the normalized height of the liquid film during the WIJH process, which was used to indicate the concentration change to analyze the concentration effect. h0 in the original                   the photographs before and after the spreading of the liquid on the GF (Fig. R2, using a Video contact Angle analyzer (Dataphysics, OCA20)). The normalized height was obtained by the simulation of the evaporation in the WIJH, as it is hard to precisely record by experiment within a low height changing from several micrometers to nanometers in a short sub-second duration.
To clearly display the trend of the nucleation in the diagram, these particle densities were further normalized to that of the sample prepared at the initial stage (0.25 s). It is a common method in other works (e.g., Sci. Adv. 6, eabd4045 (2020)).
3. Authors have discussed the WIJH synthesis mechanism and the difference on the growth of HKUST-1 for the various synthesis conditions, have some different found in nucleation or growth mechanism for the WIJH compared with the conventional bulk-heating-based methods or solvothermal method? R: Thank you. Temperature and concentration are essential elements of reaction kinetics and thermodynamics that affect the crystallization. The WIJH approach proposed a new confined interfacial heating mechanism to accelerate and control the nucleation and growth of the nanomaterials on the solid-solution interface. There are three obvious differences in nucleation and growth mechanism/process, when compared with conventional methods: 1) the synergistic mechanism between enhanced temperature and concentration; 2) the successive, ultrafast, and programmable nucleation and growth processes; 3) the formation for the final product of a flat and fusing film of one-layer HKUST-1 particles. In conventional bulk-heating-based methods, within a slow heating process and drastically-decreased concentration of the precursors, nucleation, and growth are simultaneous, slow, and random, and the final products present as rugged films of randomly stacked or intergrown particles. Below are the detailed comparison and discussion.
In conventional bulk-heating-based methods, including solvothermal synthesis, heating is a slow and near-equilibrium process with the thermal conduction from the bulk solution to the specific substrate. Therefore, the thermal field for the reaction is determined by the heat-related properties of the bulk solution, which generally presents as limited temperature (<200 °C, the boiling point of the solvent), low ramping (e.g., 4 °C min -1 for a solvothermal autoclave) and cooling rates, as well as the poor controllability of the thermal distribution. As for the concentration of the reactants, it drops rapidly and dramatically as the reaction consumes in the sealed reaction system. The limited heating and concentration would slow down the crystallization kinetics considerably (Chem. Rev. 112, 933, (2012); J. Mater. Chem. A 8, 7633 (2020)). Particularly for the synthesis on the substrate with limited nucleation sites, the heterogeneous crystallization on the substrate was further hindered by the preferential and competitive consumption of energy and precursors by the homogeneous crystallization in the bulk solution. Therefore, these methods generally suffer from long reaction time (several hours to days), poor controllability, and heavy consumption of energy and reactants. Besides, the nucleation and growth occur simultaneously and randomly, producing the products of rugged films of randomly stacked or intergrown particles with a broad size distribution.
In WIJH synthesis, stemming from the powerful electrothermal effect of the GF and a thin-layer liquid film for heat confinement, the WIJH system possesses high reaction temperature (e.g., up to 300 °C for the synthesis of HKUST-1), high heating rate (around 300 °C s -1 ) and cooling rate (approximately 200 °C s -1 ). The simultaneous evaporation of the solvent can concentrate the precursors, which timely compensates the consumed precursors to ensure a relatively-high concentration. With the synergy between the enhanced temperature and concentration, the nucleation and growth events are successive, and exponentially accelerated from several hours to sub-seconds. The high temperature by Joule heating of the GF induces the initial nucleation, The drastic evaporation caused by Joule heating markedly elevates the concentration of the precursors, and thus, induces the burst of the nucleation. In the following growth stage, with the synergy of the concentrated precursors by ongoing evaporation, high temperature at the plane interface enables fast growth and induces the formation of the unique fusing film. This synergistic mechanism is new and apparently different from conventional bulk heating.
Besides, as the heat was generated and confined around the substrate interface, the nucleation and growth on the substrate were significantly promoted and controlled by the modulation of the temperature (programming the electrified procedures). As a result, WIJH enabled the customization of the products' amount, size, and morphology. To our knowledge, this has never been realized in conventional bulk-heating-based methods, particularly in a short second-scale time.
In summary, WIJH realized the acceleration and control of the nucleation and growth on the solid-solution interface based on a unique mechanism of confined interfacial heating of the synergy between temperature and concentration effects. It endows the WIJH approach with super-efficiency, controllability, and university for the wet-chemical syntheses of various nanomaterials. The asprepared HKUST-1/GF film consisting of one-layer fusing particles displayed superior performances and efficiency in the controllable capture and liberation towards CO2. The above discussion has been summarized and emphasized in the revised manuscript.
4. How did authors obtain the specific value of the normalized quantity in Fig. 3a? R: Thank you. The quantity (revised as density) in Fig. 3a (i.e., Fig. R4) was obtained as the statistical quantities of the HKUST-1 particles divided by the area of the GF, according to the SEM images of different HKUST-1/GF samples obtained with one to six pulses in Fig. R5. The particle densities were calculated to be 0, 47 ± 21, 239 ± 100, 808 ± 197, 1847 ± 250, and 2988 ± 510    2 GF by 1, 2, 3, 4, 5, and 6 pulses, respectively. Afterward, these densities were normalized to that of the sample prepared by two pulses.
We revised "the normalized quantity" as "the normalized particle density" to avoid ambiguity. The detailed calculation method was added in the characterization part of the supplementary information.

Fig. R4
Pulse-cycle-based modulation towards particle density. From top to bottom are the electrified procedure (the current pattern), the temperature profile of the WIJH system, statistical results of the particle density that normalized to the value of the sample prepared within two pulses, and the typical SEM images of the HKUST-1/GF (the border color of the image was used to mark              5. Achieving the large-scaled synthesis using Joule heating method is significant for industrial production, thus I recommend that the authors provide more experiment content and discussion on the roll-to-roll Joule-heating continuous fabrication. R: Thank you. We have supplemented the detailed experimental parameters and additional experiments on the roll-to-roll continuous fabrication in the revision. The practicability of the continuous fabrication of a fusing film, dispersed nanoparticles, and a multi-layer intergrown film has been investigated. Besides, we have developed a layer-by-layer fashion to further control and scale up the fabrication for potential industrial production. Below are the details: Experiment content: The continuous production was demonstrated on a roll-to-roll Joule-heating fabrication system. The system mainly consists of two pairs of parallel graphite electrodes (interval distance of 7 cm), two controllable micromotors to roll the electrodes with the speed of 10 rpm, and a d.c. power source (ITECH, IT65220) connecting with the electrodes via two electric brushes (Fig. R6-a). A continuous GF strip with a width of 2 cm was clamped and passed through the rotating electrodes. The precursor solution of HKUST-1 (85 mM Cu(NO3)2 and 55 mM H3BTC) was spread on the GF to form a thin-       -2 , on the area between the electrodes). Afterward, an instantaneous current flow (24 A, 6 V) was applied to the electrodes to conduct the WIJH synthesis. Finally, the film was collected, followed by washing and drying. For the layer-by-layer fashion, the HKUST-1-coated GF was cycled into the area between two electrodes by the micromotors. A series of repeating procedures of the addition of the precursor solution on the same region of the GF and the WIJH synthesis were conducted successively until completing the fabrication.

Responses to Reviewer #2:
This manuscript reports the synthesis of materials using Joule heating method. These materials are often prepared by the wet-chemistry that involves a longer synthesis time and large usage of reactants/solvent etc. By placing a thin layer of synthesis precursor on the heating medium, a carbon file, the authors claimed that the materials including MOFs, COF, metal, metal oxide and sulfide were prepared within sub-second. Overall this is a very interesting work since the synthesis method is new and the formed materials morphology is quite different from the conventional thermal synthesis. We sincerely appreciate the reviewer for the positive and valuable comments on the manuscript. We have tried our best to address these issues. A point-by-point response to the reviewer's comments is provided below.
Specific comments are listed below.
(1) The materials synthesized by this Joule heating method are simple and easy to crystallize. For example, ZIF-8, HKUST etc does not need very harsh conditions to synthesize. From this point of view, it is hard to see the obvious advantages of the Joule heating method for wet-chemistry synthesis of solid materials. R: Thank you. The reason why we chose HKUST-1 as the model to display the WIJH synthesis is that it is one of the most extensively studied MOFs materials. Moreover, it is not very easy to be synthesized on the specific substrate, which generally requires a solvothermal reaction around/above 100 °C for up to 56 h. Compared with current methods for synthesizing HKUST-1 on the substrate, WIJH presents apparent advantages in the superefficient synthesis of exponentially reduced time, energy and reactants costs, and programmability towards the nucleation and growth. Beyond HKUST-1, other materials that generally require harsh conditions for crystallization, for instance, heating above 120 °C for 3-7 days to form TPB-DMTP-COF, and heating at 80-120 °C for up to 24 h to form MIL-88A, have also been successfully synthesized in a sharply-decreased second-scale time. These also illustrate the advantages and the university of the WIJH method to synthesize various nanomaterials under harsh or mild conditions. Below is a detailed comparison.
1) Exponentially improved synthesis efficiency of HKUST-1 on the substrate Following the reviewer' comment, we have taken a comprehensive survey on the crystallization conditions for HKUST-1 on the substrate (Supplementary Table 2). Generally, heating and/or surface modification/activation of the substrate have been widely adopted, as it is not very easy to form HKUST-1 on the substrate, especially for inert substrates like graphene film with limited nucleation sites (Adv. Mater. 27, 7293 (2015); J. Mater. Chem. A 5, 1948 (2017); ACS Appl. Mater. Interfaces 11, 22714 (2019). The synthesis begins with copper salt and H3BTC in water, ethanol, and DMF solvents, and is conducted around/above 100 °C for up to 56 h. When comparing with these previously-reported methods, WIJH exhibited remarkable advantages in the ultrafast growth rate of 1.97 µm s -1 (up to 10 5 times faster), the ultralow energy cost of 9.55  10 -6 kWh cm -2 (down to 10 -6 times lower), and ultrahigh mass production efficiency of 1660 µg s -1 (up to 10 4 times higher) without any surface treatments ( Fig. 1h and Supplementary Table 2).
Control experiments also confirmed the advantage. As shown in Fig. R9-a, under the typical solvothermal conditions, more blue precipitations of HKUST-1 were found in the solution rather than on the GF, leaving an ultralow surface coverage ratio of HKUST-1 around 6% after 60 min. In contrast, 100% coverage of HKUST-1 on the GF could be achieved as fast as 0.25 s by WIJH synthesis (Fig. R9-b). The low efficiency of solvothermal synthesis is mainly ascribed to the priority of homogeneous crystallization in heating bulk solution, and the limited reaction temperature and drastically-decreased concentration of the precursors limit the kinetics considerably.
Besides, WIJH enabled the crystallization of HKUST-1 on the GF with ultralow concentrations of the precursors (0.85 mM Cu(NO3)2 and 0.57 mM H3BTC, Fig. R9-d), which is two hundred times lower than conventional methods. In contrast, via conventional solvothermal synthesis, no particles could be found on the GF or in the solution within the same conditions (Fig. R9-c). The above clearly presents the advantages of the WIJH approach in ultrahigh synthesis efficiency of exponentially reduced time, energy and reactants costs. 2) Innovative programmability of the wet-chemical synthesis in the second-scale time Beyond the improvement in growth rate, WIJH also realized the control of nucleation and growth on the solid-solution interface via programming the electrified procedures. To our knowledge, this has never been realized in conventional bulk-heating-based methods, particularly in a short secondscale time. This could be used to customize the products' amount, size, and morphology.
3) Besides HKUST-1, other materials that required harsh conditions were also synthesized in (sub-)seconds Besides, other materials that require heating for several minutes to hours to crystallize, including ZIF-8, MIL-88A, TbBTC, TPB-DMTP-COF, Au, MnO2, and CdS, have also been synthesized by the WIJH approach in a sharply-decreased (sub-)second time. Particularly, COF is not easy to crystallize, which generally requires harsh conditions of heating above 120 °C for 3-7 days or powerful energy input to promote the crystallization (Nat. Chem. 7, 905 (2015); Nat. Syn. 1, 87 (2022)). However, the crystallization was realized in 0.95 s by WIJH. (2) The materials' synthesis solution is quick small. During the Joule heating, the evaporation of solvent should have a significant effects on the materials crystallization and growth. The authors mentioned a bit on this effect, but I think this effect should be more obvious than what has been claimed in the manuscript. Control experiments should be done to clarify the dominating mechanism (e.g., Joule heating versus solvent evaporation) in the synthesis. R: Thank you. We agree with the reviewer that solvent evaporation significantly affects material crystallization, which is also a feature of our WIJH approach. Evaporation could assist in the rapid temperature ramping, spatially confine the products toward the substrate to increase the load, and concentrate the precursors to accelerate the crystallization. Precursor concentration is the most crucial effect of evaporation in the WIJH synthesis, and is obviously different from that of conventional sealed bulk-heating-based reaction systems, where the monomer concentration decreases rapidly and dramatically as the reaction proceeds. Temperature (heating) and concentration (evaporation) are the two most important factors of the confined interfacial heating mechanism for ultrafast yet programmable crystallization. They affect and are coupled together along the whole WIJH process, synergistically accelerating and controlling the crystallization. Specifically, they display different characteristics in different crystallization stages according to our recording along the WIJH process ( Fig. 2a and Fig. 2b): a            reduction of the solvent and the corresponding sharply elevated monomer concentration in            tried our best to conduct a series of control experiments to simulate these characteristics, and their effects have been confirmed respectively. Below is the detailed discussion, using the typical WIJH synthesis of HKUST-1/GF under 3 A as the model:    (the initial 0.25 s): within powerful and rapid Joule heating, temperature rapidly increases from 23.9 °C to 115 °C. Monomer concentration also increases after the mixture but is generally lower than the critical concentration of nucleation within limited evaporation (the normalized height of the liquid film decreases to 81%). Therefore, the Joule-heating-caused high temperature is expected to dominate this stage, inducing the initial crystallization. To confirm its In our case, temperature remains almost unchanged at around 120 °C, leading to a rapid and intense evaporation event in this stage (the normalized height of the liquid film sharply decreased from 81% to 22%). This is expected to markedly elevate the monomer concentration to exceed the critical nucleation concentration and cause the nucleation burst. Therefore, we have designed control experiments to confirm the concentration effect via comparing the nucleation rates obtained by different initial concentrations of the precursors under the same temperature (Fig. R11). The increasing precursor concentrations were used to simulate the evaporation-caused concentration. As the concentrations of Cu(NO3)2 increased from 1.7 to 85 mM, the average nucleation rates increased from 85.5 to 318.2 nm s -1 , confirming the concentration effect in the nucleation stage.    (0.55-0.95 s): Due to the rapid consumption by nucleation, monomer concentration declines to a level below the critical concentration of nucleation. While the temperature of the WIJH system increased sharply within the ongoing heat input. Therefore, we investigate the temperature effect on the growth, by collecting the products obtained within the same nucleation conditions but at different growth temperatures. These experiments were conducted by programming the electrified procedures of an initial pulse of 3 A for 0.55 s for nucleation, followed by the pulse of different current intensities to achieve different temperatures (Fig. R12-a). As shown in Fig. R12-b, the average growth rates increased from 227.5 to 1697.5 nm s -1 , as the final temperature increased from 166 to 289 °C. It confirms that the temperature plays a critical role in the growth. Meanwhile, the ongoing evaporation could further compensate for the consumption of the precursors, enabling a high concentration for fast growth. Besides, as discussed in the original manuscript, the high-temperature plane of GF also mainly induced the formation of a unique fusing film consisting of one-layer particles. In summary, evaporation is the result of confined interfacial heating in an open reaction system, which promotes crystallization in terms of rapid ramping, spatial confinement, and precursor concentration. As two essential elements of reaction kinetics, temperature (heating) and concentration (evaporation) accelerate and control the WIJH synthesis synergistically. Control experiments confirmed the Joule heating effect in initial incubation, evaporation-caused concentration effect on the burst of nucleation, and high-temperature-induced growth and formation of the unique fusing film. Note that although we have discussed the most remarkable effects in different stages respectively, temperature and concentration actually participate and affect the whole WIJH crystallization process. As they are coupled together and affect mutually, it is difficult to clearly distinguish the specific contribution of high temperature and concentration on the crystallization. The above new experimental results and discussion were supplemented in the revised manuscript and supplementary information. temperature throughout. As a result, the normalized particle density increased from 1 particle per  2           2 GF for six pulses, while the particle size remained around 450 nm.
2) Higher-intensity pulse with high temperature promotes nucleation, while milder pulse benefits growth Besides, as shown in Fig. R15-b, a high-intensity pulse with a high temperature in a short time (5.25 A, 300 °C, 0.25 s) would lead to burst nucleation, producing smaller particles around 491 nm. While under a low-intensity pulse with a low temperature for a long duration (1.85 A, 184 °C, 5 s), a few particles were produced in the nucleation portion, leaving sufficient reactive species unreacted. Afterward, the growth proceeded and became preferable over time. As a result, larger particles around 1281 nm were synthesized.
The above details and discussion have been added to the revised manuscript and supplementary information. c d e f Fig. R15 a) Pulse-cycle-based modulation towards particle density and b) pulse-intensity-based modulation towards particle size. From top to bottom are the electrified procedure (the current pattern), the temperature profile of the WIJH system, the statistical results of a) the particle density (normalized to the value of the sample prepared within 2 pulses) and b) the particle size, and the typical SEM images of the HKUST-1/GF (the border color of the image was used to mark the            

Responses to Reviewer #3:
In this work, Zhang et al. reported a wet-interfacial Joule heating approach for synthesis of nanomaterials on conductive carbon films like graphene films. A very thin liquid layer is coated on the graphene film and the Joule heating rapid bring it to a high temperature to trigger the reaction. They synthesized various nanomaterials such as MOF, COF, metal nanoparticles, oxide nanoparticles, etc. And they demonstrated the application of the MOF films for CO2 uptake and the application of the Joule heating method for temperature swing adsorption. We sincerely thank the reviewer for the professional and careful comments. These insightful suggestions are very constructive to improve our work. We have tried our best to revise our manuscript accordingly, and the point-by-point responses are provided below.
Main concerns: 1. One main concern of this method is the scalability. The reaction happens at the interface between the graphene film and the solution; thus, the solution must be a very thin layer. This seriously limit its production rate and scalability compared to the bulk solution synthesis method. As demonstrated                  to scale up the process? Maybe a continuous process? R: Thank you. As the procedure is simple, and the devices are accessible, the WIJH approach could be scaled up readily for the continuous and mass fabrication of nanomaterials with the aid of a roll-to-roll Joule-heating setup. The practicability of the continuous fabrication of a fusing film and dispersed nanoparticles have been demonstrated, giving the production rates around 14.7 cm 2 s -1 and 25 cm 2 s -1 . The estimated production rate for the fabrication of nanomaterialscoated films (around 265 m h -1 ) is superior to that reported by one of the latest advances in rapid production of MOFs    -1 in a batch experiment in lab scale, Adv. Sci. 7, 2002190, (2020)). Note that 2 µL is a typical condition for synthesizing 0.2 cm 2 HKUST-1/GF. It is enough to achieve 100% coverage of HKUST-1 on the substrate to complete the preparation, and less requirement towards the precursors is one of the advantages of the WIJH synthesis. Besides, we have also developed a layer-by-layer fashion to further control and increase the mass loading of the MOFs on the substrate (from ~1.13 to ~4.67 g m -2 ), thereby improving the mass efficiency of the fabrication for potential industrial production. Below are the details: The continuous fabrication system mainly consists of two pairs of parallel graphite electrodes (interval distance of 7 cm), two controllable micromotors to roll the electrodes with the speed of 10 rpm, and a d.c. power source (ITECH, IT65220) connecting with the electrodes via two electric brushes (Fig. R16-a). A continuous GF strip with a width of 2 cm was clamped and passed through the rotating electrodes. The precursor solution of HKUST-1 (85 mM Cu(NO3)2 and 55 mM H3BTC)                -2 , on the area between the electrodes). Afterward, an instantaneous current flow (24 A, 6 V) was applied to the electrodes to conduct the WIJH synthesis. Finally, the film was collected, followed by washing and drying.
For one batch of fabrication of HKUST-1/GF, both fusing HKUST-1 film (Fig. R16-b) and dispersed nanoparticles (Fig. R16-c) could be obtained by altering the electrified procedures, giving the production rates around 14.7 cm 2 s -1 and 25 cm 2 s -1 , respectively. The estimated production rate for the fabrication of nanomaterials-coated films (around 265 m h -1 ) is superior to that reported by one of the latest advances in           -1 in a batch experiment in a lab scale, Adv. Sci. 7, 2002190, (2020)). Moreover, the fabrication could be In our WIJH approach, the WIJH synthesis could be scaled up by a roll-to-roll continuous fabrication to give the mass per batch of 1.58-6.54 mg. The production efficiencies of 1376-1660 µg s -1 were up to 10 4 higher than other methods. As for the energy cost based on the mass, WIJH also exhibited a low energy cost of around 1.07 10 -4 kWh per mg MOFs) compared to other works (approximately 3.9 10 -3 to 7.25 kWh per mg MOFs). Moreover, the mass of the product could be further increased by scaling up the substrate, increasing the concentration of the precursors, or increasing the volume of the precursors with the increase of the power for a batch. As mentioned above, the less requirement of the precursor solution is one of the advantages of WIJH synthesis. A microliter of the precursor solution is enough to achieve 100% coverage of nanomaterials on the substrate in our WIJH approach (e.g., 2µL for 0.2 cm 2 GF). The large-volume bulk solution has been widely adopted in conventional methods. However, most of them are wasted for fabricating nanomaterials on the substrate.
Besides, we also provided the comparison based on the area of the substrate (Fig. 1h). The area information was facile to be collected in the experimental parts in the literature. More importantly, it could reflect the production efficiency objectively and comprehensively for             -1 is up to 5 orders of magnitude faster than other typical heating-based methods (Table R2), while the energy cost of 9.55  Stemming from the unique confined interfacial heating mechanism of the synergy between temperature effect and concentration effect, we could control the nucleation and growth of the nanomaterials on the GF, thereby customizing the product size. We have successfully obtained small HKUST-1 nanoparticles of 54 ± 11 nm and large HKUST-1 microparticles of 1.65 ± 0.2 µm, through simultaneously adjusting the pulse intensity (i.e., the temperature) and the initial concentrations of the precursors. Below is the detailed discussion: Generally, the particle size is highly correlated to the crystallization process, which is affected by the reaction temperature, time, and concentration (Chem. Rev. 112, 933, (2012); Angew. Chem. Int. Ed. 60, 26390, (2021); Nat. Chem. 5, 203, (2013)). According to the LaMel model, a rapid and intense nucleation event leads to small particles by depleting the precursors, while larger particles are obtained when growth is favorable. In the WIJH approach, a high-intensity pulse with high temperature enabled intense nucleation of MOFs, while a low-intensity pulse allowed a favorable growth event. Therefore, we realized the control of particle size via programming electrified procedures, obtaining particles with sizes ranging from 1281 ± 267 nm to 491 ± 100 nm by increasing the current intensities from 1.85 A to 5.25 A (Fig. 3b). On the other hand, as the initial concentration of the precursor of copper salt increases from 0.85 mM to 170 mM (with the same 3:2 molar ratio of Cu(NO3)2 and H3BTC), the particle size increases from 207 ± 52 nm to 1208 ± 271 nm (Fig. 3c). Combining the above routes, we have successfully synthesized small HKUST-1 nanoparticles with the size of 54 ± 11 nm under a high-intensity pulse and low precursor concentrations (5.25 A, 0.85 mM Cu(NO3)2 and 0.56 mM H3BTC, Fig. R18-a). Large microparticles with the size of 1.65 ± 0.2 µm were successfully synthesized under a low-intensity pulse and high precursor concentrations (1.85 A, 170 mM Cu(NO3)2 and 110 mM H3BTC, Fig. R18-b).
Besides, benefitting from the ultrafast and successive nucleation and growth in the WIJH process, the particle was relatively uniform with a narrow size distribution. This contrasts sharply with the broad size distribution obtained by conventional solvothermal syntheses. 5. The authors demonstrate the CO2 uptake and liberation cycle by the Joule heating process ( Figure  5). What is the mechanism of the Joule heating-induced liberation? R: Thank you. The CO2 uptake and liberation by HKUST-1/GF are based on a temperature swing adsorption process, in which the adsorption occurs at low temperature, while the desorption occurs at high temperature with a supply of electrified procedure to the HKUST-1/GF. HKUST-1 could strongly adsorb CO2 with the electrostatic interactions under low temperature. It is an exothermic physical process. The kinetic energies of the adsorbed CO2 and HKUST-1 are higher within the rapid thermal conduction from the GF to HKUST-1 under Joule heating. This causes a corresponding increase in their interaction at the interface, thereby reducing the effective area of HKUST-1 available for adsorption (ACS Appl. Mater. Interfaces 10, 34802 (2018)). Therefore, as shown in Fig. R19, the uptake would decrease in the CO2 adsorption isotherm, and the amount of adsorbed CO2 decreases as the temperature increases (i.e., a higher electrified input toward HKUST-1/GF). After cutting off the current, the temperature of the GF and HKUST-1 dropped sharply, and thus, HKUST-1 could adsorb CO2 again, completing a desorption-adsorption cycle. The mechanism for the Joule-heating-based liberation of the adsorbed CO2 has been added in the revised manuscript. 6. What is the energy cost of the Joule heating induced CO2 desorption and how does it compare to temperature swing enabled by other thermal processes, as well as other pressure swing process? R: Thank you. In an interfacial Joule heating (IJH) process based on HKUST-1/GF, the energy for the desorption of 1 cm 3 CO2 was estimated to be 3.72 10 -4 kWh (the full desorption of 9.2 cm 3 g -1 CO2 with power of 5.95 w for 200 s, green region in Fig. R19). It is lower or comparable with other previously-reported thermal processes (Sep. Purif. Technol. 309, 123053 (2023)); ChemSusChem 13, 2089 (2020)).
Generally, temperature swing adsorption is considered a low-cost and energy-saving route for the desorption of CO2, when compared with other swing processes, e.g., pressure swing adsorption (Acc. Chem. Res. 50, 778 (2017); Chem. Eng. J. 383, 123075 (2020)). However, the low thermal conductivity of the adsorbents, e.g., most microporous MOFs, would hinder this process and strongly increase energy consumption (Adv. Mater. 28, 1839, (2016)). In our interfacial Joule heating strategy, the Joule heat around GF was directly transferred to the CO2-adsorbed MOFs. The direct and compact contact between GF and HKUST-1 could sharply shorten the heat transfer distances, improving desorption efficiency. As for the comparison with other thermal processes, e.g., microwave, and magneto-thermal processes, Joule heating is known as a simple, highly-efficient, and energy-saving heating strategy. GF possesses ultrahigh electrothermal conversion efficiency (>99%), due to the low heat capacity and appropriate electrical conductivity. It sharply decreases energy consumption. Moreover, the IJH strategy presents high controllability towards the adsorption and desorption, which is hard to realize in conventional methods.
The above discussion has been added to the revised manuscript.
7. Will the precursors also be evaporated during the synthesis process since the synthesis temperature is so high (>300°C)? And the organics maybe be destroyed under this high temperature. R: Thank you. The precursors of organics and salts would not be evaporated or decomposed. In our WIJH approach, the heating temperature of the WIJH system was set to be less than the thermal decomposition temperature of the product to avoid thermal destruction. The ultrahigh temperature (e.g., 300 °C) only occurs at the graphene film interface, while precursors exist in the solution part where the temperature is lower than their respective decomposition temperatures. Using the synthesis of HKUST-1 as the model, we have supplemented the thermogravimetric analysis (TGA) to investigate the thermal decomposition behaviors of both precursors and product, and collected XRD patterns to confirm there are not any decomposed products of the precursors in the final products. Fig. R20-a shows the TGA curves of the precursors of H3BTC and Cu(NO3)2·2.5H2O and the product of HKUST-1/GF. H3BTC and HKUST-1 possess high decomposition temperatures around 340 °C and 300 °C, respectively. Cu(NO3)2·2.5H2O exhibits two distinct stages of mass loss ranging from 132 to 176.2 °C and 207.6 to 290.2 °C, which are ascribed to the dehydration and the thermal decomposition to form copper oxide (J. Therm. Anal. Calorim. 147, 5599 (2022); J. Therm. Anal. 45, 1381 (1995)). As shown in Fig. R20-b, in the case of the growth of HKUST-1 on the GF, the temperature profile of the WIJH system ranges from ~25 to ~285 °C, which comprises the temperature of the GF (~25 to 288 °C) and the solution layer (~25 to ~153°C). Within the ultrafast consumption of the precursors for crystallization, the precursors dissolved in the solution part throughout. As its highest temperature (153 °C) is lower than the initial thermal decomposition temperatures of Cu(NO3)2 (207.6°C) and H3BTC (300 °C), precursors would not be decomposed. Besides, the coordination between precursors spontaneously occurs after mixing. Their strong interactions would increase the thermal stabilities of the precursors, and thus, reduce their volatilization, evaporation, and even decomposition (Nat. Commun. 14, 2294 (2023)).
Furthermore, no characteristic peaks indexed to the precursors' decomposition products were found in the XRD pattern of HKUST-1/GF (Fig. 1g), which further indicated that precursors were not decomposed.
The above results have been discussed in the revision. Minor points: 1. Supplementary Fig. 5 is not discussed in the main text. R: Thank you, and sorry for the negligence. Supplementary Fig. 5 was involved in the supplementary discussion 3, and we have marked the supplementary Fig. 5 in the revision.
2. Line 217, the authors mentioned that the particles could fuse together to form a film consisting of monolayer MOF particles. There is no evidence that the film is "monolayer". R: Thank you. As shown in Fig. R21, the cross-sectional SEM image of the HKUST-1/GF indicates that the HKUST-1 film was composed of one layer of fusing HKUST-1 particles. To avoid the ambiguity for monolayer, we have updated the expression as "the film consisting of one layer of fusing MOF particles" in the revised manuscript. 3. PDF reference card should be provided for all the XRD patterns. R: Thank you. All PDF reference cards for the XRD patterns have been provided in the revised manuscript and supplementary information.
HKUST-1 by the roll-to-roll Joule heating method. To evaluate the uniformity of the HKUST-1 film across the substrate, we have collected SEM images from different sites along the length direction of the upscaled sample (the distance of each collecting site was about 2 cm). As shown in Figure  R1-a, all the samples exhibited similar morphologies of flat fusing films, indicating a relatively uniform distribution of the nanomaterials in a long range. The above results and discussion have been added in the supplementary information in red. 3. Figure R18a, the particle size is too small on this scale. I suggest zoom-in on the SEM image to provide better resolution. R: Thank you. The figure has been replaced by magnified SEM images of the sample to display the particle size ( Figure R2, i.e., Supplementary Fig. 26). 5. Figure 1c inset, scale bar required for the sample size. R: Thank you. Figure 1c (Figure R3) has been updated as follows, in which the scale bar of the inset has been added.